The present disclosure is related to the field of artificial valves, and more specifically to an implantable, sutureless valve graft comprising a biomaterial. The disclosure is further related to a method for suturelessly bonding a biomaterial to a bioprosthetic frame.
Prosthetic stents and valves have been described in the prior art. Stents have been used with success to overcome the problems of restenosis or re-narrowing of a vessel wall. Valves are exemplified by U.S. Pat. No. 5,258,023 (to Roger), in which a prosthetic valve is taught that is constructed of synthetic materials.
However, the use of such devices is often associated with thrombosis and other complications. Additionally, prosthetic devices implanted in vascular vessels can exacerbate underlying atherosclerosis.
Research has focused on trying to incorporate artificial materials or biocompatible materials as bioprosthesis coverings to reduce the untoward effects of metallic device implantation. Such complications include intimal hyperplasia, thrombosis and lack of native tissue incorporation.
Synthetic materials for stent coverings vary widely, e.g., synthetic materials such as Gore-Tex®, polytetrafluoroethylene (PTFE), and a resorbable yarn fabric (U.S. Pat. No. 5,697,969 to Schmitt et al.). Synthetic materials generally are not preferred substrates for cell growth.
Biomaterials and biocompatible materials also have been utilized in prostheses. Such attempts include a collagen-coated stent, taught in U.S. Pat. No. 6,187,039 (to Hiles et al.). As well, elastin has been identified as a candidate biomaterial for covering a stent (U.S. Pat. No. 5,990,379 (to Gregory)).
In contrast to synthetic materials, collagen-rich biomaterials are believed to enhance cell repopulation and therefore reduce the negative effects of metallic stents. It is believed that small intestinal submucosa (SIS) is particularly effective in this regard.
Bioprosthetic valves combining synthetic and biological materials have also been studied. For example, U.S. Pat. No. 5,824,06 (to Lemole); U.S. Pat. No. 6,350,282 (to Eberhardt); and U.S. Pat. No. 5,928,281 (to Huynh) teach bioprosthetic heart valves that may employ an aortic valve (comprising animal or patient tissue) sutured to an artificial valve frame.
Some of the above-discussed coverings, while used to prevent untoward effects, actually exacerbate the effects to some extent. Accordingly, it is desirable to employ a native biomaterial or a biocompatible material to reduce post-procedural complications.
A mechanically hardier valve graft device is required in certain implantation sites, such as cardiac, aortic, or other cardiovascular locations. In order to produce a sturdier bioprosthesis, a plurality of layers of biomaterial may be used. Suturing is a poor technique for joining multiple layers of biomaterial. While suturing is adequate to join the biomaterial sheets to the metallic frame, the frame-sutured multiple sheets are not joined on their major surfaces and are therefore subject to leakage between the layers. Suturing of the major surfaces of the biomaterial layers introduces holes into the major surfaces, increasing the risk of conduit fluid leaking through or a tear forming in one of the surfaces.
Heretofore, biomaterials have been attached to bioprosthetic frames, e.g., stents and valves, using conventional suturing techniques. As well, the primary methods available for securing prostheses to tissue (or tissue to tissue) involved the use of sutures or staples. However, this approach is disadvantageous from manufacturing and implantation perspectives.
Suturing is time-consuming and labor-intensive. For example, suturing a sheet of biomaterial over a stent frame typically is an operator-dependent process that can take up to two hours for trained personnel. Because suturing is manually performed, there are concerns relating to manufacturing uniformity and product reliability. As well, suturing entails repeatedly puncturing the biomaterial, creating numerous tiny holes that can weaken the biomaterial and potentially lead to leakage and infection after the graft device has been installed.
Moreover, the presence of suture material can enhance the foreign body response by the host patient, leading to a narrowing of the tubular vessel in which the graft is implanted.
A recent attempt to provide a “sutureless” heart valve prosthesis, U.S. Pat. No. 6,287,339 (to Vazquez, et al.), while providing a valve device to be attached to patient tissue without the use of sutures, nevertheless continues to require sutures to secure the active portion of the prosthesis to its abutment structure.
Biocompatible adhesive compounds and photochemical cross-linking agents have been investigated as alternatives to suturing. For example, fibrin glue, a fibrinogen polymer polymerized with thrombin, has been used as a tissue sealant and hemostatic agent.
Bioadhesives generally produce rigid, inflexible bond regions that can lead to local biomaterial tears and failure of the graft device. In addition, some bioadhesives and photochemical cross-linking agents carry risk of acute and chronic toxicity and bio-incompatibility.
The invention will become more readily apparent from the following detailed description, which proceeds with reference to the drawings, in which: